The invention relates to polymer resins incorporating filler materials of particle size 1-100 nm and having a narrow particle size distribution.
It is well known that the presence of fillers in a polymer resin can improve mechanical and chemical properties of the resin. For example, Moloney et al. (Journal of Materials Science, 1987, 22, 381) reported that, in epoxy systems, by increasing the volume fraction of fillers and by using higher modulus fillers, such as micron-size silica, alumina, and silicon carbide, the modulus of the composites was also increased. Filled or reinforced polymers have been used for many years in applications as varied as synthetic rubbers, epoxy-fiberglass composites, and paints.
However, despite the advantages of using filled polymers in such application, in many cases, the properties fall short of the ideal. For example, articles fabricated from or coated with polymers, filled or unfilled, are easily scratched. Plastics used in optical applications such as eyeglass lenses are typically coated to improve scratch resistance, yet resistance to scratching remains less than desired. A second example is magnetic tape, which is also susceptible to scratching, leading to a loss in quality. In addition, conventional fillers can embrittle polymers.
Therefore, there is a continuing need for polymers with improved properties, including scratch resistance. There is also a need for polymers having increased modulus while maintaining good ductility. There is a further need for polymers having improved dimensional stability.
It has been unexpectedly discovered that incorporation of a filler of very small particle size with a narrow particle size distribution results in a polymer having improved mechanical properties, including increased toughness and scratch resistance and improved dimensional stability.
In one aspect, the present invention relates to a polymer nanocomposite comprising about 50-99 weight % polymer resin and about 1-50 weight % nanoparticles having particle size from about 1 nm to less than about 100 nm, and a narrow particle size distribution. The polymer resin is preferably an epoxy, polycarbonate, silicone, polyester, polyether, polyolefin, synthetic rubber, polyurethane, nylon, polystyrene, polyphenylene oxide, and polyketone or a copolymer or blend thereof. More preferably, the polymer resin is an epoxy. Even more preferably, the epoxy is a diglycidyl ether of bisphenol A. The nanoparticles are preferably metal nanoparticles, metal oxide nanoparticles, metal nitride nanoparticles, metal carbide nanoparticles, metal sulfide nanoparticles, metal fluoride nanoparticles, and metal chloride nanoparticles, more preferably, metal oxide nanoparticles, and even more preferably, titanium dioxide nanoparticles. Preferably, the particle size of the nanoparticles ranges from about 1 nm to about less than 50 nm. Preferably, the polymer nanocomposite comprises about 70-5 weight % polymer resin and about 5-30 weight % nanoparticles having particle size from about 1 nm to less than about 100 nm, and a narrow particle size distribution.
In another aspect, the present invention relates to an epoxy nanocomposite having improved mechanical properties comprising 50-99 weight % epoxy resin and 1-50 weight % quasi-spherical particles having particle size from about 1 nm to less than about 100 nm and a narrow particle size distribution.
In yet another aspect, the invention relates to a scratch-resistant coating comprising about 50-99 weight % polymer resin and about 1-50 weight % nanoparticles having particle size from about 1 nm to less than about 100 nm, and a narrow particle size distribution. In a preferred embodiment, the scratch-resistant coating comprises about 85-95 weight % polymer resin and about 5-15 weight % nanoparticles.
In yet another aspect, the invention relates to a polymer nanocomposite stamp comprising about 50-99 weight % polymer resin and about 1-50 weight % nanoparticles having particle size from about 1 nm to less than about 100 nm, and a narrow particle size distribution. In a preferred embodiment, the polymer nanocomposite stamp comprises about 85-95 weight % polymer resin and about 5-15 weight % nanoparticles.